Hyponatremia : ACEi vs CCB

Symptoms

• presented with signs and symptoms of hyponatremia (eg, nausea, malaise, headache, lethargy, seizures, coma, respiratory depression) 
• decreased serum sodium levels (101-109 mEq/L)

ACE Inhibitors

• Frequency is unreported
• ACE inhibitors alone can precipitate hyponatremia without co-administration of thiazide diuretics
• hyponatremia induced by ACE inhibitors appears to be dilutional and is accompanied by features of SIADH
• discontinuing the ACE inhibitor leads to resolution of the hyponatremia
• Patients may show hypokalaemia if thiazide or loop diuretics are used concomitantly with ACE inhibitors
•  

Mechanism & Risk

• It is postulated that ACE inhibitors at low doses cannot block the conversion of angiotensin I to angiotensin II in the brain. Increased circulating angiotensin I is converted to angiotensin II in the brain causing thirst stimulation and consequently SIADH.
• risk for hyponatremia may be greater in patients on concomitant diuretic therapy or who have congestive heart failure.

Calcium Channel Blockers

• In theory, calcium channel antagonists with natriuretic properties could cause hyponatremia.
• A case of amlodipine-associated hyponatremia has been reported.
• calcium channel antagonist– related hyponatremia, if it exists, is extremely rare.

Management

• In mild to moderate cases with a normovolaemic fluid status clinically, ceasing the offending drug and gentle fluid restriction would improve serum sodium levels gradually within a week.
• In an acutely unwell patient due to severe drug induced hyponatraemia, severe fluid restriction or infusion of hypertonic saline may be require
• May consider changing therapy and monitoring patient for improvement

Alternatives

• Diuretics are not recommended as have higher likelihood of causing hyponatremia
• ARBs are also established to cause hyponatremia and no available data on comparison with ACEi
• Beta Blockers- Beta blockade, especially of the Beta 1 receptor at the macula densa, inhibits renin release, & the release of aldosterone. This causes hyponatermia and hyperkalemia

References:

1. http://www.gpnotebook.co.uk/simplepage.cfm?ID=x20120201092040500242
2. https://www.pjms.com.pk/issues/aprjun207/article/casereport3.html
3. Jenny A. Van Amburgh. Can Lisinopril Cause Hyponatremia? - Medscape - Jul 28, 2011
4. American Journal of Kidney Diseases, Vol 52, No 1 (July), 2008: pp 144-153